Method for making copper plated aluminum wires

ABSTRACT

Aluminum is extruded, and the resulting core when still warm is lined with copper by deforming a copper tape around the core, welding the tape edges and drawing the resulting tube onto the core, and possibly further to obtain wire of desired diameter.

United States Patent Ziemek 1451 Mini, 1n, 1971.

METHOD FOR MAKING COPPER PLATED ALUMINUM WIRES Gerhard Ziemek, Hannover, Germany 1 1 Kabel-und Metallwerke Gutehofinungshutte Aktiengesellschaft, Hannover, Germany Feb. 2, 1970 Inventor:

Assignee:

Filed:

App]. No.:

Foreign Application Priority Data Feb. 13, 1969 Germany ..P 19 07 1079 US. Cl "29/4741, 29/473.3, 29/488 ..1.......B2ld 39/04 Field of Search ..29/474.3, 473.9 474.1, 488,

References Cited UNlTED STATES PATENTS Carlson et a1 ..29/473.3 Alexander..... ..29/474.1 X

Nast et a1. ..29/488 M Pendelton et a1, 29/4733 X Frost "29/4741 X Polizzano ..29/474.1 X Vansteenkisto ..29/474.3 Belalou et al. .....29/488 X Dion...., ...29/474.l Stout et all. ..29/474.l

Primary Examiner-John F. Campbell Assistant Examiner-Richard Bernard Lazarus Attorney-Smyth, Roston & Pavitt ABSTRACT Aluminum is extruded, and theresulting core when still warm T is lined with copper by deforming a copper tape around the core, welding the tape edges and drawing the resulting tube onto the core, and possibly further to olbtain wire of desired diameter.

4 Claims, 1 Drawing Figure METHOD FOR MAKING COPPER PLATED ALUMINUM WIRES The invention relates to a method of making so-called copper-clad, aluminum wires comprising a wire core element of aluminum with a coating or lining of copper.

Copper-clad aluminum wires have the particular advantage of comparably low specific weight, and they combine economy resulting from use of inexpensive aluminum with good electric properties of copper. For making such wires, it is known, for example, to provide a copper tube, to fill the same with aluminum, and to draw the resulting structure in a manner known per se, so that the diameter is reduced to the desired dimension. In order to avoid formation of cavities which would be detrimental to the homogenity of the resulting wire, it is necessary that the pipes used are of limited length. Therefore, continuous manufacturing of copper-clad wires in this manner is not possible. Furthermore, it was found that at temperatures equal to or above the melting temperature of the aluminum, the diffusion of copper into aluminum is considerable. The resulting diffusion layer has harder consistency so that the subsequent drawing requires particular precautions.

In accordance with another method it is known to provide an aluminum wire and two copper tapes of predetermined length. The copper tapes are deformed around the aluminum wire so that the wires become enclosed in two half cylinders, running in longitudinal direction parallel to each other and to the aluminum wire. Subsequently, the edges of the two half cylinder-copper tapes are welded to form a sleeve. The thus formed copper sleeve is then applied to and drawn onto the aluminum wire core to obtain a smaller diameter. In addition, it has been suggested to provide an aluminum wire core, to continuously deform a copper tape to as to establish a sleeve, and to weld adjoining edges of such tape. Subsequently, the sleeve diameter is reduced by drawing, at least down to the diameter of the aluminum wire.

The present invention proceeds in a different manner for manufacturing copper lined or clad aluminum wire. The copper-plating, lining or coating is also to be made from a deformed copper tape which is being welded to provide a tube or sleeve around the aluminum core. However, in accordance with the present invention, an extrusion press is provided for producing a continuously running and extractable aluminum string to serve as aluminum core. As the extruded aluminum core is still warm, it is clad with a copper sleeve, there being a tape running longitudinally into the production line, and being deformed to establish a tubular sleeve around the aluminum string. 'I'hat copper tape or sleeve is welded along its edges and subsequently the copper tube is reduced in diameter by drawing it onto the aluminum wire. The aluminum core with copper tube applied may subsequently be reduced further in diameter to obtain the desired dimensions of the wire of the wire to be produced. This way, it is possible to provide copperclad aluminum wire in a single working step though serially operating stages may be provided.

A faultless, mechanically firm connection is established between the copper coat and the aluminum core if one proceeds in accordance with the teaching of this invention. During the production of copper-clad wires in accordance with known methods an oxide layer forms usually on the aluminum core which layer is partially destroyed only during the diameter reduction step or has to be removed in a separate step. In order to impede or to inhibit formation of an oxide layer it is of particular advantage to extract the aluminum core from the press in a protective gas environment, and preferably the subsequent coating of the core by lining it with copper tape is likewise carried out in a protective gas atmosphere. In other words, the uncovered aluminum core, from the point where leaving the extrusion press up to the point where the copper lining is closed, should traverse a protective gas at mosphere, that part of the production line being enclosed accordingly.

The temperature of the aluminum core as it leaves the press is approximately 400 C. It was, therefore, found advisable to produce some cooling for the extracted string. For example,

cool air or any other suitable medium such as the protective gas may be used to reduce the temperature of the pressed aluminum string to 200 to 300 C. Operating temperatures within that range were found to be most suitable for manufacturing of wire, particularly for providing and applying the copper tube as lining to the aluminum core.

The copper tape used for tube forming and cladding is preferably taken from a suitable supply by means of rolls which in a more or less continuous process deform the copper tape to provide a tubular sleeve around the aluminum core, in longitudinal direction and parallel thereto. Considering that the copper tape is relatively thin, withdrawing and transporting of the formed copper tube or sleeve can be provided before as well as behind the welding electrodes of welding equip ment which welds the edges of the tape to close the tube. This way the resulting tube can be guided very precisely which is a prerequisite for accurate welding of the edges of the tape. Also, guiding the tube before and behind the welding area relieves the welding area proper from tensile stress and strain.

A caterpillar type transportation and advancing equipment may be used here, which is known per es, and which has brackets or jaws gripping the tube, but they open when the tube traverses the welding area for access of the welding electrode, and they close again behind the welding area. As was briefly mentioned above, the copper-clad aluminum wire can be drawn for obtaining diameter reduction in one of several steps. The wire is drawn for the diameter reduction behind the welding equipment, for example, through one or several die members such as thrust collars, the pulling being provided by a withdrawal disk.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof wiil be better understood from the following description taken in connection with the accompanying drawings in which:

The FIGURE shows somewhat schematically a side elevation of a production line for making copper-clad wire in accordance with the preferred embodiment of the present invention.

An aluminum string or core 2 is extruded by and from a press I. Care is being taken that, for example, by means of suitable ventilation or the like the extruded core 2 is cooled to obtain a temperature below the temperature of extrusion. By way of example, the aluminum core when leaving the press, may have a temperature of 400 C., and it is cooled to a temperature of 200 to 300 C.

Parallel to the extrusion of core 2 a copper tape l is reeled from a supply reel or drum 3 and guided. into the path of core 2 to run at similar speed in juxtaposition and parallel thereto. By means of suitable deformation rolls (not shown) tape 4 is shaped to wrap around and to envelope core 2 so as to finally form a tubular sleeve 5, lining string 2.

The thus formed tube 5 is not closed but the two long edges of the tape face each other along the extension of the newly formed sleeve. These edges are welded together by means of suitable welding equipment 6, the welding being preferably carried out in a protective gas atmosphere.

A caterpillar withdrawal device '5' is provided to transport the tube (and the core) and pull the tube through the production line. Caterpillar '7 has individual jaw elements ii, firmly gripping the tube to exert force thereupon and to pull the stringsleeve arrangement particularly through a die member 9. This die member 9 may be a thrust collar which is provided behind the welding equipment 6, and by cooperation with caterpillar device 7 the diameter of tube 5 is reduced so that the copper tube 5 is applied to and drawn onto aluminum core 2. Additionally, die member 9 may provide further reduction in overall diameter. Die member 9 may have an appropriately selected, small aperture, so that the caterpillar arrangement draws also the string to a tube to reduce its diameter. Thus, it is possible, in one step to draw the tube 5 to be applied onto core 2 and to draw also the latter, with tube 5 being likewise drawn additionally, to remain in intimate contact with the aluminum core.

However, in the illustrated embodiment die member 9 as cooperating with caterpillar 7 is assumed to draw only tube 5 to be applied onto core 2. Additionally, there is a second drawing stage provided which includes a second die 10, providing for the diameter reduction of the tube-core arrangement. In particular, the die 10 may be provided with an aperture smaller than the aperture in die 9 and the resulting diameter of the copper-lined wire is equal to the desired wire diameter to be produced. The drawing and pulling force is provided in this second stage by a withdrawal and take-up disk 11. Subsequently, the resulting copper-clad aluminum wire is wound upon a take-up and supply drum or reel 12.

An additional, similar caterpillar may be provided merely to pull the tube 5 through the welding area, gripping the sleeve before and behind the welding equipment but having its jaws open to permit the welder 6 to perform its function.

It should be mentioned that it may well be advisable to provide proper enclosure means into which core 2 is extruded from press 1 so that the string runs exclusively in protective gas atmosphere, up to the point of lining it with copper tape 4 and closing the resulting tube around the core. That gaseous atmosphere may, in addition, be used as the coolant, to obtain ing departures from the spirit and scope of the invention are intended to be covered by the following claims.

I claim:

vl. Method for producing wires with aluminum core and copper linings, comprising the ateps of:

extruding an aluminum core, the extruded aluminum core having relatively high temperature; providing parallel to the extruded aluminum core a copper lining the aluminum core when still at a temperature above 200 C. from the extrusion as sole source of heating, with the copper tape by deforming the copper tape in a protective gas atmosphere to produce a tube around the still warm aluminum core;

welding the edges of the copper tape immediately thereafter, for closing the tube;

applying the copper tube onto the aluminum core immediately following closing the tube, by drawing the tube onto the aluminum core to obtain diameter reduction thereof; and

drawing aluminum with copper tube for further diameter reduction to obtain a copper-clad aluminum wire.

2. The method as in claim 1, including the step of providing temperature reduction for the extruded aluminum string to a temperature in the range of about 200 to 300 C.

3. The method as set forth in claim 2 and including the step of cooling the extruded aluminum core.

4. The method as in claim 1 the steps being carried out in the stated sequence. 

2. The method as in claim 1, including the step of providing temperature reduction for the extruded aluminum string to a temperature in the range of about 200* to 300* C.
 3. The method as set forth in claim 2 and including the step of cooling the extruded aluminum core.
 4. The method as in claim 1 the steps being carried out in the stated sequence. 